Originally posted by Marc Sabatella If the choice is between getting a fast enough shutter speed or accepting motion blur, I'd shoot anything wide open - it's bound to be sharper than if I stopped down. That include the kit zooms, although of course I'd prefer to shoot something faster to increase shutter speed further.
Bottom line being, whatever you lose in sharpness by shooting wide open on even the worst lenses I've used is more than offset by the increase in shutter speed, at least in the cases where that's the limiting factor. And besides, my choice in lens is primarily determined by focal length, so I don't care how sharp my DA15 is wide open if it's not the right lens for the job.
So I still don't really get the question.
Of course you don't get the question Marc, you live in sunny Colorado.
Here in dreary overcast Nebraska I find myself shooting in low light a lot, whether I'm shooting people in downtown Omaha under awnings in the old market, wildlife in wooded areas, or in early/late light, etc. Bottom line is I'm usually wanting to increase shutter speed to freeze action, but often can't because there isn't enough available light. And that's with ISO jacked up on the K-5 to 1600 to 6400 and as wide an aperture as I can by with, for my application and the lens I'm shooting. For example, this weekend I was shooting sandhill cranes in the afternoon with my 300mm wide open at ISO 1600 and I often wasn't able to get above 1/750 shutter speed, which left BIF wingtips blurry.
So I posed the question because I'm trying to find lenses that will work for me wide open. For arguments sake lets say the DA * 50-135 is not as sharp as the Sigma 50-150 at f/2.8. That I'd have to stop down the DA to f/4 to get it as sharp as the Sigma. Then that would be one on the plus side for the Sigma.
I just thought if I could compile a list of lenses that people find acceptably sharp wide open, it would help me with lens choices. I realize sharpness is but one quality of a lens, but it's an important one to me, even if that makes me a not so cool photographer.